Generally, in the previous process of manufacturing a liquid crystal display, millions of thin film transistors are formed on a substrate through an epitaxial method to serve as control units. However, if the quality of part of the thin film transistors cannot achieve the desired effect during manufacturing, the switching control characteristic cannot be presented, so that the defect of bright spots or dark spots will be produced, and thus the quality of the liquid crystal display will be significantly reduced. Therefore, the thin film transistors must be effectively tested to maintain the quality of the liquid crystal display.
In the existing solutions for testing the thin film transistors of the display, for the structure of connecting test signal lines on the peripheral area of a TFT array substrate with test pads, reference may be made to FIG. 1. As shown in FIG. 1, a test signal line M1 on the peripheral area of the substrate passes through a passivation layer via hole V1 through which ITO is connected with the test signal line M1 and a passivation layer via hole V2 through which ITO is connected with a test pad lead M2, and then is connected with the test pad lead M2 and further connected to a corresponding test pad P. It could be seen from the figure that, in the process of connecting different test signal lines M1 to the corresponding test pads P through the test pad leads M2, the test pad leads M2 will have to run across other test signal lines M1. Electrostatic discharge is easily caused in the crossover process of the test signal lines M1 and the test pad leads M2, so that the test signal lines M1 and the test pad leads M2 will be in short circuit with each other. In this case, the test signal lines are short-circuited and no detction can be performed, thus reducing the yield of a product.
Therefore, a solution is needed to solve the problem that the test signal lines and the test pad leads are easily in short circuit with each other in the prior art, reduce the injury risk of electrostatic discharge, improve the test accuracy of the product, and then improve the yield of the product.